The present invention relates to an improved animal containment system utilizing audio and electric stimulation to control the location of livestock and other animals.
U.S. Pat. No. 5,408,956, incorporated herein by reference, describes a new livestock control alternative that uses animal ear tags to administer audio and electric stimuli when an animal enters the range of a field transmitter. In this prior art system, the transmitter continuously generates a stimulation code that is received by an ear tag receiver when the ear tag containing the receiver enters the effective range of the transmitter. Tests have proven the effectiveness of this system, but also have identified the sensitivity of transmitter range to varying environmental conditions. On a given signal power setting transmitter range (and thus the exclusion range) tends to vary (sometimes significantly) over time.
U.S. Pat. No. 5,241,923, incorporated herein by reference, describes an electronic inclusion system using a series of transponders to define the boundary of an area within which animals are to be restrained. A substantial shortcoming of this system, however, is that environmental changes in transmitter range could result in gaps between the areas covered by adjacent transmitters.
Both of these systems are designed to exclude (or include) all animals from (or within) the specified areas. In many cases, however, it is not appropriate to treat all animals alike. It may be desirable to move certain animals into a defined area, while excluding other animals from that area. Neither of the prior art systems provides a means for selective exclusion or inclusion of identified animals or suggests the desirability of such selective treatment.
Similarly, it is highly desirable to have the capability of confirming the presence of animal within a specified area. The only means of doing so, however, requires physical observation of the animals and their identifying markings. There is no effective system for electronically verifying the presence of animals.